Method of hydrostatically extruding compound material and compound billets

ABSTRACT

In the hydrostatic extrusion of compound billets, in which the billet is formed of a core of one material and a casing surrounding the core of another material, and in which a gap is left during the assembly of the billet to allow for deformation of the casing, the core is provided with a point and the casing has an inwardly directed conical flange within which the point of the core rests. At the back end, the core is provided with a sealing device for preventing the entry of fluid into the space between the core and the casing. In order to prevent the compression of the air in the space between the core and the casing, the core is provided at its front end with passages which open into the point of the core and which communicate with the space between the core and the casing, providing an air escape arrangement.

United States Patent [191 Korsell et al.

[ Feb. 18, 1975 1 METHOD OF HYDROSTATICALLY EXTRUDING COMPOUND MATERIAL AND COMPOUND BILLETS [75] lnventors: Torsten Korsell; Hans Larker; Erik Lundblad; Jan Nilsson, all of Robertsfors, Sweden [73] Assignee: Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden 221 Filed: Jan. 29, 1974 21 Appl. No.: 437,652

[30] Foreign Application Priority Data Jan. 30, 1973 Sweden 73012452 [52] US. Cl 29/474.3, 72/60, 72/258, 29/1875 [51] Int. Cl B21d 39/04 [58] Field of Search.... 72/60, 258; 29/4743, 473.3, 29/1875, 191, 479

[56] References Cited UNITED STATES PATENTS 3,316,630 5/1967 Goedecke et al 29/4743 3,364,561 l/l968 Barrington 29/4733 3,751,957 8/1973 Nilsson 72/60 3,777,362 12/1973 Nilsson et al. 29/4743 Primary Examiner-Richard .1. Herbst [57] ABSTRACT In the hydrostatic extrusion of compound billets, in which the billet is formed of a core of one material and a casing surrounding the core of another material, and in which a gap is left during the assembly of the billet to allow for deformation of the casing, the core is provided with a point and the casing has an inwardly directed conical flange within which the point of the core rests. At the back end, the core is provided with a sealing device for preventing the entry of fluid into the space between the core and the casing. in order to prevent the compression of the air in the space between the core and the casing, the core is provided at its front end with passages which open into the point of the core and which communicate with the space between the core and the casing, providing an air escape arrangement.

PATENTEDFEBI 8% 3,866. 306

Fig.

METHOD OF HYDROSTATICALLY EXTRUDING COMPOUND MATERIAL AND COMPOUND BILLETS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing rods, wire or tubes of compound material having a core of one material and a casing surrounding the core of another material, by means of hydrostatic extrusion, and a billet for use in this method. By hydrostatic extrusion is meant a process in which a billet is placed in a pressure chamber where it is surrounded by a liquid pressure medium in which such a pressure is generated that the material is forced out through a die having an opening giving a product having the desired cross-section. The method is primarily intended to be used for extruding compound material comprising a core of aluminum or aluminum alloy and a casing of copper, copper alloy or of an aluminum alloy having a composition different from that of the core. However, it can also be used for other combinations of materials.

2. The Prior Art A billet of suitable shape comprises a core having a conical point and a casing surrounding the core. This casing is suitably shaped at one end as a truncated cone so that the casing is axially positioned with respect to the core. At the rear end of the billet is a seal which prevents pressure medium from penetrating into the gap between the core and the casing. Usually the billet has a plug of a hard material, normally steel, at the rear end this plug covering the end surfaces of the casing and core and axially positioning the core. The seal may consist of a hat or ring which bridges the joint between the plug and the casing.

The two U.S. Pat. Nos. 3,654,687 and 3,620,059 describe hydrostatic extrusion of compound products in more detail.

Certain practical difficulties have been found to exist in combining a core and a easing into one billet if the clearance between them is small. This is particularly so when the casing consists of a copper tube. Deformation of shape cannot be avoided when annealing and machining copper tubes. They easily become oval or bent and easily acquire small dents during annealing and handling. It may then be difficult or impossible to insert the core into the casing ifthe clearance is small. Therefore such large clearance has been chosen that normal deformation occuring during annealing and handling does not impede the insertion of the core. The large volume of air which is then enclosed in the gap, around 2,000 cm a for billets of normal sizes, may cause problems during the extrusion process, resulting in patches where the adhesion between the casing and the core material is unsatisfactory. Water deposited from the air as it is compressed as the dew-point temperature drops during compression of the gap prevents satisfactory adhesion between core and easing material.

U.S. Pat. No. 3,777,362 suggests arranging an air pocket at the rear end of the billet so that the air in the gap can flow into this pocket when the casing is pressed against the core as the pressure increases in the pressure chamber. In order to prevent such a pressure increase and to prevent precipitation of water in the gap completely when the tube is compressed, if the air enclosed has normal humidity, the air pocket must be so large that the pressure after compression of the tube is less than the precipitation pressure. In this connection normal humidity means the humidity which can practically be maintained in the premises where a core and a casing are combined into a billet. It has been found advisable to have an air pocket the volume of which is at least 25% of the volume of the gap, that is, an air pocket with a volume of 500 cm From the practical point of view an air pocket of this size is much too big and results in a useless space which decreases the possible volume of the billet correspondingly.

SUMMARY OF THE INVENTION According to the present invention, the air in the gap between the core and the casing is evacuated as the pressure is increased in the pressure chamber so that the casing is pressed into contact with the core, thus preventing any pressure increase which would result in precipitation of water. This evacuation is effected by providing a billet of the type described with a channel in its front part, leading from the gap between the easing and the core and opening into or in front of the easing at the point of the core. The channel may consist of one or more grooves at the transition point between the cylindrical part of the core and its point or of a groove inside the conical front part of the casing, said groove extending at least as far as the cylindrical part of the casing. The channel may also comprise one or more apertures in the front part of the billet. To increase the chances for air in the gap to reach said channels even if the front part of the casing is pressed into contact with the core earlier than the rear part, the

core or casing may be provided with one or more axial grooves, at least along the greater part of its length.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further described with reference to the accompanying drawings.-

FIG. 1 shows schematically a section through a pressure chamber with a billet in place and FIG. 2 shows on a larger scale the front part of a billet of alternative design, and a die.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings 1 designates a press table and 2 a pressure generating piston in a hydraulic press, not 0therwise shown, in which there is a cylinder to operate the piston 2.

A high pressure cylinder 3 comprises a steel cylinder 4, a strip sheath 5 of pre-stressed rectangular strips having high strength, end pieces 6, seals 8 and 9 and a spacing sleeve 7 to keep the seals axially positioned in the cylinder 4. The cylinder 8, piston 2 and a die 10 form a pressure chamber. In the pressure chamber is a billet 11 comprising a core 12 of aluminum or alumi num alloy and a casing 13 of copper or a copper alloy. Suitable alloys are naturally used in the manufacture of products intended to conduct current. The casing often becomes somewhat oval and bent during annealing. The outer diameter of the core 12 and the inner diam eter of the casing 13 are shown so that the core can easily be inserted into the casing even if the casing has been deformed to a normal extent during annealing and handling. A gap 14 will be formed between the core and the casing. A suitable radial clearance for a core diameter of mm is generally between 1 and 5 mm.

The clearance is thus considerable and likewise the volume of the gap and the air enclosed therein. A steel plate 15 is inserted at the rear end of the billet. A hatshaped seal 16 of elastomeric material surrounds the rear part of the billet, covering the joint between the plate 15 and the casing 13 and thus preventing the surrounding pressure medium 17 from penetrating into the gap 14. The plate 15 has a shoulder 18 whichprojects into the tube. The shoulder is bevelled along the surface 19. The outer diameter of the shoulder 18 is greater than the inner diameter of the casing 13. Thanks to the shoulder, the plate 15 can be pressed into the casing 13 and expand it when the billet is being put together. This expansion provides good axial positioning of the plate in the casing. The front part of the casing is cut to form a truncated cone 20 which is in abutment with the conical point 21 of the core 12 and thus positions the core axially with respect to the eas- The embodiment according to FIG. 1 shows an axial channel 22 with its mouth at the point of the core outside the conical-part 20 of the casing 13, and a radial channel 23 intersecting the channel 22 and having its mouth in the cylindrical part of the core, that is, in the gap 14. The channels may have a diameter of about Thus, the gap 14 communicates with the space 24 between the front part of the billet and the die 1.0, providing a means of evacuation when the casing 13 is pressed against the core 12 under the influence of the pressure medium 17. The core is provided with an axial groove 25 through which air can flow from the rear part of the billet if the casing should be pressed into contact with the core at the front of the billet first.

In the embodiment according to FIG. 2, grooves 26 are provided in the core 12 at the transition between its cylindrical part and the point 21. The space 14 will therefore communicate with the space 24 through the grooves 26. One to four grooves have a width of l to 2 mm have been found to be suitable for billets with a core diameter'of 150 mm. The core may be provided with axial grooves 27 but this is not absolutely necessary. It is advisable to make the point 21 of the core blunter than the inlet cone 29 of the die to provide free outlet from the grooves 26 as long as possible. This embodiment also has the advantage that, because of plastic deformation thegrooves are sealed before the point 21 of the core has been entirely pressed into contact with the inlet cone 29 of the die. This prevents lubricant in the inlet cone of the die from being pressed in through the grooves 26 into the gap 14, which would completely prevent adhesion between the casing and the core in the extruded product.

As mentioned before, the invention may also be used for manufacturing tubes. Obviously the core then con-:

sists of a tube.

We claim:

1. Method of manufacturing rods, wire or tubes of compound material having a core of one material and a casing surrounding the core of another material,

nal diameter than the external diameter of the core part, so that a space exists within the casing on the outside of the core part, said casing part being shaped as a truncated cone at one end, said cone securing the core part axially wi th respect to the point of the casing -part, and sealing means at the rear end of the billet for preventing pressure medium from penetrating into a gap formed between the core part and easing part which comprises inserting said billet in a pressure chamber and pressing it by a surrounding pressure medium through an opening in a die giving a product having the desired cross-section, in which one of the parts of the .billet (11) has an air-escape channel opening adjacent the point (21) of the billet into the die opening which communicates with said space by which the air enclosed between the core part (12) and the casing part (18) is expelled from the billet (11) when the casing part (13) is forced into contact with the core part (12) during the extrusion process.

2. Billet for forming rods, wires or tubes of compound material by hydrostatic extrusion, comprising a core part of one material having a conical point, a casing part of another material surrounding the core part of substantially greater internal diameter than the external diameter of the core part, so that a space exists within the casing part on the outside of the core part, said casing part being shaped as a truncated cone at one end which is in contact with the conical point of the core part and easing part and axially positions the core part with respect to each other, and sealing means at the rear end of the billet to prevent pressure medium from penetrating into the billet, one of the parts of said billet having an air-escape channel therein adjacent the point (21) of the billet (11) leading from the space (14) between the Vgasi part (13) and the core part (12) and opening into the conical point (21) of the billet (11) outside of the foremost conical section (20) of the casing part (13).

3. Billet according to claim 2, in which the channel comprises an axial groove (26) in the core part (12) at the transition between its point (21) and its cylindrical portion, the mouth of said groove (26) being located outside the conical point (20) of the casing part and in the space (14) between the core part (12) and the easing part (13).

4. Billet according to claim 2, in which the channel comprises a groove on the inside of the conical point (20) of the casing part (13), extending so far into the billet (11) that its mouth is in the space (14) between the core part (12) and the casing part (13).

5. Billet according to claim 2, in which the channel comprises an aperture (22,23) in the core part (12) opening into the point (21) of the core part (12) outside the front (20) ofthe casing part and at the cylindrical portion of the core part (12) in the space (14) between the casing part (13) and the core part (12).

6. Billet according to claim 2, in which the channel comprises an aperture in the truncated cone (20) of the casing part.

7. Method of manufacturing rods, wire or tubes of compound material having a core part of one material and a casing part surrounding the core part of another material, which comprises hydrostatically extruding a billet comprising a core part having a conical point, a casing part surrounding the core part of substantially greater internal diameter than the external diameter of the core part, so that a space exists within the casing part on the outside of the core part, said casing part being shaped as a truncated cone at one end, said cone securing the core part axially with respect to the point of the casing part, and sealing means at the rear end of the ing the desired cross-section, and which comprises expelling air from said space through an opening in one of said parts into the die opening during the extrusion process. 

1. Method of manufacturing rods, wire or tubes of compound material having a core of one material and a casing surrounding the core of another material, which comprises hydrostatically extruding a billet comprising a core part having a conical point, a casing part surrounding the core part of substantially greater internal diameter than the external diameter of the core part, so that a space exists within the casing on the outside of the core part, said core part being shaped as a truncated cone at one end, said cone securing the casing part axially with respect to the point of the core part, and sealing means at the rear end of the billet for preventing pressure medium from penetrating into a gap formed between the core part and casing part which comprises inserting said billet in a pressure chamber and pressing it by a surrounding pressure medium through an opening in a die giving a product having the desired cross-section, in which one of the parts of the billet (11) has an air-escape channel opening adjacent the point (21) of the billet into the die opening which communicates with said space by which the air enclosed between the core part (12) and the casing part (18) is expelled from the billet (11) when the casing part (13) is forced into contact with the core part (12) during the extrusion process.
 2. Billet for forming rods, wires or tubes of compound material by hydrostatic extrusion, comprising a core part of one material having a conical point, a casing part of another material surrounding the core part of substantially greater internal diameter than the external diameter of the core part, so that a space exists within the casing part on the outside of the core part, said casing part being shaped as a truncated cone at one end which is in contact with the conical point of the core part and axially positions the core part with respect to each other, and sealing means at the rear end of the billet to prevent pressure medium from penetrating into the billet, one of the parts of said billet having an air-escape channel therein adjacent the point (21) of the billet (11) leading from the space (14) between the casing part (13) and the core part (12) and opening into the conical point (21) of the billet (11) outside of the foremost conical section (20) of the casing part (13).
 3. Billet according to claim 2, in which the channel comprises an axial groove (26) in the core part (12) at the transition between its point (21) and its cylindrical portion, the mouth of said groove (26) being located outside the conical point (20) of the casing part and in the space (14) between the core part (12) and the casing part (13).
 4. Billet according to claim 2, in which the channel comprises a groove on the inside of the conical point (20) of the casing part (13), extending so far into the billet (11) that its mouth is in the space (14) between the core part (12) and the casing part (13).
 5. Billet according to claim 2, in which the channel comprises an aperture (22,23) in the core part (12) opening into the point (21) of the core part (12) outside the front (20) of the casing part and at the cylindrical portion of the core part (12) in the space (14) between the casing part (13) and the core part (12).
 6. Billet according to claim 2, in which the channel comprises an aperture in the truncated cone (20) of the casing part.
 7. Method of manufacturing rods, wire or tubes of compound material having a core part of one material and a casing part surrounding the core part of another material, which comprises hydrostatically extruding a billet comprising a core part having a conical point, a casing part surrounding the core part of substantially greater internal diameter than the external diameter of the core part, so that a space exists within the casing part on the outside of the core part, said core part being shaped as a truncated cone at one end, said cone securing the casing part axially with respect to the point of the core part, and sealing means at the rear end of the billet for preventing pressure medium from penetrating into a gap formed between the core part and casing part, which comprises inserting said billet in a pressure chamber and pressing it by a surrounding pressure medium through an opening in a die giving a product having the desired cross-section, and which comprises expelling air from said space through an opening in one of said parts into the die opening during the extrusion process. 